InstantOutboxPublisher

The publisher will emit an event upon the creation of the instant outbox. Having an event emitted upon the outbox creation enables us handle an instant outbox processing in separate transactions. We can listen for the published event after transaction is committed, and then we can process the outbox by calling TransactionalOutbox.processInstantOutbox.

The implementation is specific to the framework that uses the library so the caller needs to provide the specifics.

The publisher is required so that an instance of TransactionalOutbox is created using the TransactionalOutboxBuilder.

Example of the publisher implementation on Spring framework:

class InstantOutboxPublisherImpl(
  private val applicationEventPublisher: ApplicationEventPublisher,
) : InstantOutboxPublisher {

override fun publish(event: InstantOutboxEvent) =
  applicationEventPublisher.publishEvent(
    SpringApplicationEvent(
       source = this,
       payload = event.outbox
      )
    )
}

Example of a listener on Spring framework:

class AfterCommitEventListener(
  private val transactionalOutbox: TransactionalOutbox
) {

  @TransactionalEventListener(phase = TransactionPhase.AFTER_COMMIT)
  fun handle(event: SpringApplicationEvent) {
    transactionalOutbox.processInstantOutbox(event.payload)
  }
}